The present invention generally relates to accurate and time-efficient motion tracking for time-resolved imaging and motion artifact compensation in imaging systems. The present invention specifically relates to an optical motion sensor incorporating one or more optical fibers embedded in a body contour conforming matrix.
Motion artifacts are caused by motion of an imaged object or a part of the imaged object during an imaging of the object. Thus, patient motion during a sequential acquisition of image frames of the patient may cause motion artifacts in the displayed image of the patient. More particularly, the patient may voluntary move or experience involuntary movements (e.g., respiration, cardiac motion and blood flow, eye movements and swallowing) during the image frame sequence, and such patient movements may result in blurring and/or ghosting within the displayed image of the patient. Accurate and time efficient motion tracking is therefore critical for motion compensation of motion artifacts in imaging systems.
However, motion tracking is highly dependent on the capabilities of the imaging system itself (e.g., an X-ray fluoroscopic system, a three-dimensional ultrasound system ("3D US"), a time-resolved magnetic resonance imaging system ("MRI"), and a computed tomography system ("CT")). Typically, motion tracking of this kind is limited by the imaging frame rate (e.g., 12Hz for 3D US) and can involve special acquisition sequences and processing overhead (e.g., tracking pulse sequence interleaved with imaging sequences in MRI). Additionally, for each imaging modality, there is further ability to integrate electrocardiogram, respiratory, and other physiological signals as gating triggers during image frame acquisition and/or image reconstruction. Motion tracking and subsequent compensation is therefore time consuming and is often less accurate than intrinsically high-frame rate imaging (e.g., motion compensated CT reconstruction vs. real-time echo for cardiac imaging).
The present invention, as compared to current motion tracking systems, offers an optical motion sensor for high accuracy, real time patient position information that can potentially increase image quality and shorten the image acquisition time. More particularly, the present invention allows for tracking and compensation of motions intrinsic to the target of interest that are directly reflected in the optical motion sensor.
One form of the present invention is an optical motion sensing system for use in imaging an anatomical structure. The optical motion sensing system employs the optical motion sensor and a motion tracker with the optical motion sensor including a body contour conforming matrix ("BCCM") and one or more optical fiber(s). For purposes of the present invention, the term "anatomical structure" is broadly defined herein as any structural feature of a human body or an animal body, whether external or internal or accessed externally or internally. Examples include, but are not limited to, body torso/limbs and organ systems.
Upon being adjoined to the anatomical structure, the BCCM structurally conforms, partially or entirely, to a surface contour of the anatomical structure for reciprocating any motion by the anatomical structure. More specifically, the BCCM may be affixed to or contiguous with the anatomical structure whereby the BCCM structural flexes, extends, expands, and/or compresses to conform, partially or entirely, to the surface contour of the anatomical structure. As such, the BCCM reciprocates, positively or negatively, any linear movement and/or angular movement by the anatomical structure, and/or any structural flexion, extension, expansion and/or compression by the anatomical structure.
Each optical fiber is embedded in the BCCM for generating an encoded optical signal indicative of a shape of the optical fiber(s) responsive to any reciprocal motion by the BCCM during an imaging of the anatomical structure.
The motion tracker is responsive to each encoded optical signal for periodically reconstructing the shape of the corresponding optical fiber(s). Each change in the shape of the optical fiber(s) between the geometric reconstructions of the optical fiber(s) represents motion by the anatomical structure during the imaging of the anatomical structure. For example, the motion tracker may reconstruct the shape of the optical fiber(s) for each frame or series of frames of an imaging of the anatomical structure whereby each change in the shape of the optical fiber(s) between each frame or series of frames represents linear and/or angular movement by the anatomical structure, and/or structural flexion, extension, expansion and/or compression by the anatomical structure.
The foregoing form and other forms of the present invention as well as various features and advantages of the present invention will become further apparent from the following detailed description of various embodiments of the present invention read in conjunction with the accompanying drawings. The detailed description and drawings are merely illustrative of the present invention rather than limiting, the scope of the present invention being defmed by the appended claims.
The following publication:
As shown in
System 10 employs an optical motion sensor 20 including a BCCM 30, one or more optical fibers 40 and a motion tracker 50. For purposes of the present invention, BCCM 30 is broadly defined herein as any article or device structurally configured for structurally conforming, partially or entirely, to a surface contour of an anatomical structure upon being adjoined to the anatomical structure (e.g., affixed to or contiguous with the anatomical structure). By structurally conforming to the surface contour of the anatomical structure, any motion by the anatomical structure is reciprocated, positively or negatively, by BCCM 30 as will be further explained herein in connection with a description of
For purposes of the present invention, each optical fiber 40 is broadly defined herein as any article structurally configured for transmitting light by means of successive internal optical reflections via a deformation optic sensor array 41, and each deformation optic sensor array 41 is broadly defined herein as any article structurally configured for reflecting a particular wavelength of light while transmitting all other wavelengths of light whereby the reflection wavelength may be shifted as a function of an external stimulus applied to optical fiber 40. Examples of optical fiber 40 and deformation optic sensor array 41 include, but are not limited to, a flexible optically transparent glass or plastic fiber incorporating an array of fiber Bragg gratings integrated along a length of the fiber as known in the art, and a flexible optically transparent glass or plastic fiber having naturally variations in its optic refractive index occurring along a length of the fiber as known in the art.
In operation with one or more optical fibers 40 embedded within BCCM 30, each optical fiber 40 generates an encoded optical signal ("EOS") 42 via deformation optic sensor array 41 as known in the art that indicates a shape of optical fiber 40 at any instantaneous shape sampling of optical fiber 40 and more particularly over the course of multiple shape samplings, indicates each change to the shape of optical fiber 40 that occurs as BCCM 30 reciprocates motion of the anatomical structure. Encoded optical signal 42 therefore facilitates a use of optical fiber 40 in visually displaying a position and orientation of the anatomical structure within a defined space at any instantaneous time, and in visually displaying a motion tracking of the anatomical structure within the defined space.
To this end, system 10 further employs a motion tracker 50 incorporating an optical interface 51, a shape reconstructor 52 and a feedback generator 53 for processing encoded optical signal 42 to thereby periodically reconstruct a portion or an entire shape of optical fiber 40. For purposes of the present invention, optical interface 51 is broadly defined herein as any device or system structurally configured for transmitting light through optical fiber 40 to receive encoded optical signal 42 as generated by the successive internal reflections of the transmitted light via deformation optic sensor array 41. An example of optical interface 51 includes, but is not limited to, an arrangement of an optical coupler, a broadband reference reflector and a frequency domain reflectometer as known in the art for transmitting light through optical fiber 40 and for receiving encoded optical signal 42 as generated by the successive internal reflections of the transmitted light via deformation optic sensor array 41.
For purposes of the present invention, shape reconstructor 52 is broadly defined as any article or device structurally configured for processing encoded optic signal 42 to partially or entirely reconstruct the shape of optical fiber 40 and for generating motion tracking data ("MTD") 54a in an appropriate format for purposes of enabling imaging system 60 to compensate for motion-induced distortions in an imaging of the anatomical structure due to movement of the anatomical structure during the imaging of the anatomical structure. More particularly, any changes in the shape of an optical fiber 40 between geometrical reconstructions of the optical fiber 40 represent motion by the anatomical structure during the imaging by system 60. As such, motion compensation data 51a informs imaging system 60 of any sensed and tracked motion of the anatomical structure whereby imaging system 60 may execute known image-motion compensation algorithms to minimize, if not eliminate, any ghosting or blurring in the imaging of the anatomical structure. High accuracy image reconstruction by imaging system 60, particularly on a low-frame rate imaging, may therefore be achieved.
An example of shape reconstructor 52 includes, but is not limited to, a reconstruction engine installed as software and/or firmware on any type of computer for implementing a known shape reconstruction technique. In particular, a known shape reconstruction technique for correlating encoded optic signal 42 into strain/bend measurements that are integrated into a shape of optical fiber 40. In practice, the reconstruction engine may be integrated into imaging system 60.
For purposes of the present invention, feedback generator 53 is broadly defined herein as any article or device for converting motion tracking data 54 into feedback data 55 for purposes of providing motion feedback to imaging system 60 and one or more feedback systems 70.
In a first exemplary embodiment, feedback generator 53 may generate and communicate closed-loop control data ("CCD") 55a to imaging system 60 for purposes of enabling imaging system 60 to automatically adjust various imaging aspects of the system. For example, closed-loop control data 55a may facilitate automatic scan adjustments by imaging system 60 involving a determination of the position of the patient relative to imaging system 60 and reconstruction of high quality images of the anatomical structured based on the patient positioning.
In a second exemplary embodiment, feedback generator 53 may generate and communicate video/audio data ("VAD") 55b to a feedback system 70 having a monitor with speakers and/or earplugs for purposes of presenting the patient with visual and/or audio feedback as to any movement by the patient during the imaging of the anatomical structure. The patient therefore may adjust his/her body positioning, psychological state and/or physical state (e.g., breathing depth and rate) as needed to facilitate an accurate imaging of the anatomical structure. Furthermore, the visual/audio feedback may include information of maximum allowed motion for accurate imaging. For example, the visual feedback may include two (2) parallel lines and a dot with the lines indicating the maximum motion allowed and the dot indicates the current position of the patient, and the audio feedback may be presented whenever the patient motion is outside the parallel lines. The patent may therefore voluntarily adjust his/her position.
In a third exemplary embodiment, feedback generator 53 may generate and communicate patient control data ("PCD") 55c to a feedback system for counteracting movement by the patient and/or controlling a positioning of the patient. For example, patent control data 55c may be converted into forces to exert on the patient via BCCM 30 or any other article or device to counter any unacceptable movement by the patient. Also by example, patent control data 55c may be converted into control signals for an interventional device (e.g., a catheter) to maintain a positioning of the patient relative to imaging system 60.
In a fourth exemplary embodiment, feedback generator 53 may generate and communicate sensing control data ("SCD") 55d to a feedback system associated with imaging system 60 or another sensing system having a feedback system 70 (e.g., an electromagnetic tracking device for a surgical instrument). For example, sensing control data 55d may be converted into signals for executing position and/or orientation changes for certain sensing elements of the imaging system 60 (e.g., MR coils) or the sensing system to optimize image quality.
An example of feedback generator 53 includes, but is not limited to, a feedback engine installed as software and/or firmware on any type of computer for implementing one or more feedback modes. In practice, the feedback engine may be integrated into shape reconstructor 52, imaging system 60 or a feedback system 70.
A description of
As shown in
The particular manner by which optical fiber 43 is embedded within BCCM 30 is dependent upon the application of optical motion sensor 21.
For example, as shown in
Alternatively or concurrently, sheath 31 may encircle a chest of patient 80 as shown in
By further example, as shown in
Referring to
A stage 92 of flowchart 90 encompasses a manual or an automatic definition of an acceptable range of motion of the anatomical structure(s) being tracked. Thus, for example, stage 92 may involve a definition of an acceptable range of linear movement and/or angular movements of the head and the chest of patient 80, an acceptable range of breathing depth and rate of patient 80, and an acceptable heart beat rate of patient 80.
A stage 93 of flowchart 90 encompasses an acquisition of an image sequence of the anatomical structure and a motion tracking for each frame or a series of frames (e.g., motion sensing/tracking every 100 frames) that facilitates a motion compensation for displaying an accurate imaging of patient 80 via an image monitor 62 and/or a closed-loop control of X-ray device 61 via a C-arm 63. Upon each reconstruction of a shape of the optical fibers, a stage 94 of flowchart 90 determines if any tracked motion of the subject anatomical structure is acceptable. If yes, then the next frame or series of frames is acquired. Otherwise, feedback as previously described herein is generated in the form of video, audio, patient control and/or system control during a stage 95 of flowchart 90.
For example, feedback monitor 71 may display two (2) parallel lines and a dot with the lines indicating the maximum motion allowed by a head of patient 80 and the dot indicates the current position of the head of patient 80. In addition, as represented by dashed lines extending from motion tracker 52 to sensors 22 and 23, feedback forces may be applied to patient 80 to control and/or maintain a positioning of patient 80.
While various exemplary embodiments of the present invention have been illustrated and described, it will be understood by those skilled in the art that the exemplary embodiments of the present invention as described herein are illustrative, and various changes and modifications may be made and equivalents may be substituted for elements thereof without departing from the true scope of the present invention. For example, although the invention is discussed herein with regard to FBGs, it is understood to include fiber optics for shape sensing or localization generally, including, for example, with or without the presence of FBGs or other optics, sensing or localization from detection of variation in one or more sections in a fiber using back scattering, optical fiber force sensing, fiber location sensors or Rayleigh scattering. In addition, many modifications may be made to adapt the teachings of the present invention without departing from its central scope. Therefore, it is intended that the present invention not be limited to the particular embodiments disclosed as the best mode contemplated for carrying out the present invention, but that the present invention includes all embodiments falling within the scope of the appended claims.
This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.